cortex, a region filled with a highly cellular connective tissue stroma and many ovarian follicles, which in the adult ovary vary greatly in size The most internal part of the ovary is the medulla, which contains loose connective tissue and blood vessels entering the organprimordial follicles—consist of a primary oocyte enveloped by a single layer of the flattened follicular cellsunilaminar primary follicle stratified follicular epithelium, the granulosa, in which the cells communicate through gap junctions. Follicle cells are now termed granulosa cells and the follicle is a multilayered primary follicle (cuboidal cells)
Multilaminar Primary FolliceZonapellucida:four glycoproteins secreted by the oocyte;bind proteins on the surfaces of sperm and induce acrosomal activation. Filopodia of follicular cells and microvilli of the oocyte penetrate the zonapellucida, allowing communication between these cells via gap junctions.
Each ovary is covered by a simple cuboidal epithelium, the germinal epithelium, continuous with the mesothelium and overlying a layer of dense connective tissue capsule, the tunica albugineagranulosa layer as the cells secrete follicular fluid accumulates, the spaces gradually coalesce antrum Follicular Fluid : hyaluronate, growth factors, plasminogen, fibrinogen, the anticoagulant heparansulfate proteoglycan, and high concentrations of steroids (progesterone, androstenedione, and estrogens) with binding proteins.Membranagranulosa (columnar)
Follicular WallsGranulosa Cells – Stratified ColumnarBM – separates TI and GTI: vacuolated and lightly stained because of their cytoplasmic lipid droplets, a characteristic of steroid-producing cells (androstenedione which is transformed in the granulosa cells as estradiol)TE: fibroblasts and smooth muscle cells continuous with stroma
Corpus luteum after ovulation (super folded)Corpus Albicans: scar of dense connective tissue called corpus albicans in the absence of pregnancy (less convoluted)
After ovulation:Granulosa cells granulosa lutein cellsaromatase conversion of androstenedione into estradiolTheca interna cells Theca lutein cells stain more darkly, with cytoplasmic ultrastructural features of steroid-synthesizing cells stimulated by LH
Atretic follicle: oocyte is detached from granulosa cellsAtresia involves apoptosis and detachment of the granulosa cells, autolysis of the oocyte and collapse of the zonapellucida. Early in this process, macrophages invade the degenerating follicle and phagocytose the debris. Occurs anytime
Mature OocyteAchievement of Polarity and Radial Symmetry
Frog OvarySource of Yolk: Digested FoodYolk Nuclei from germinal vesicle
Unfertilized egg
Second Cleavage furrow relatively shallow compared to first
Yolk is resistant to cleavage forces
CoeloblastulaEpidermal layer (highly pigmented) Skin Epithelium or Lining of nervous systemNervous Layer Neuroblasts of the Nervous SystemMarginal Zone: active conversion of yolk to cytoplasm; involved in formation of the lips of the blastoporeStill seen is the fertilization membrane (not labeled)
CoeloblastulaEpidermal layer (highly pigmented) Skin Epithelium or Lining of nervous systemNervous Layer Neuroblasts of the Nervous SystemMarginal Zone: active conversion of yolk to cytoplasm; involved in formation of the lips of the blastoporeStill seen is the fertilization membrane (not labeled)
Process: InvolutionVentral limit of the gray crescent region of formation of the dorsal lip of the blastopore
Ring of involuted marginal zone (lip) cells are collectively known as the yolk plugInvoluted dorsal lip cells endodermMore ventral and lateral to the chordamesoderm is the mesodermChordamesoderm notochord
notochord was derived from cells indistinguishable from the mesoderm at the region of the dorsal lipSomites become: 1. Dermatome dermis and appendage musculature 2. Sclerotome vertebral skeleton 3. Myotome skeletal musclesSomatic mesoderm in conjuction with the ectoderm skin with its blood and connective tissuesSplanchnic mesoderm in conjuction with gut endoderm lining epithelium, muscles, and blood vessels of the entire mid- and hindgut.